Technical Field
The present invention generally relates to the field of pulmonary treatments.
Description of the Related Art
Pulmonary diseases are some of the most common medical conditions, affecting tens of millions of people in the U.S. alone. Pulmonary diseases result from problems in the respiratory tract that interfere with proper respiration. Many of these diseases require medical attention or intervention in order to restore proper lung function and improve a patient's overall quality of life. Some of the more common pulmonary diseases include asthma and chronic obstructive pulmonary disease or COPD. Symptoms of pulmonary disease like COPD and asthma vary but often include a persistent cough, shortness of breath, wheezing, chest tightness, and breathlessness. Generally, these symptoms are exacerbated when performing somewhat strenuous activities, such as running, jogging, brisk walking, etc. However, these symptoms may be noticed when performing non-strenuous activities, if the disease is allowed to progress unchecked. Over time, especially if medical attention is not sought, a person's daily activities will be significantly impaired, thus reducing overall quality of life.
A variety of treatments are available for pulmonary diseases includes reducing exposure to harmful agents, administering medications (e.g., bronchodilators, steroids, phosphodiesterase inhibitors, theophylline, antibiotics, etc.), administering lung therapy (e.g., oxygen therapy, pulmonary rehabilitation), and surgical intervention, such as bronchial thermoplasty. While these treatments are sometimes effective, typically the treatments are not without their drawbacks. For example, pharmacological treatment requires patient compliance, can cause undesirable or even harmful side effects, and may not always treat the underlying cause of the disease. Similarly, surgical intervention can result in the destruction of smooth muscle tone and nerve function, such that the patient is unable to respond favorably to inhaled irritants, systemic hormones, and both local and central nervous system input.
A relatively new and promising treatment for pulmonary diseases is targeted lung denervation (TLD). This method utilizes ablation, such as radio-frequency (RF) ablation via an ablation assembly to selectively treat target regions inside of the airway wall (e.g., anatomical features in the stromas) and/or target areas that run to the lung along the outside of the bronchus, while protecting superficial tissues such as the surface of the airway wall. For example, the mucous glands can be damaged to reduce mucus production a sufficient amount to prevent the accumulation of mucus that causes increased air flow resistance while preserving enough mucus production to maintain effective mucociliary transport, if needed or desired. Nerve branches/fibers passing through the airway wall or other anatomical features in the airway wall can also be destroyed.
Specially designed catheters allow for the introduction of an ablation assembly, generally comprising one or more collapsible electrodes or energy emitters, coupled to an expandable member, such as a balloon, into the airway of a patient via a delivery device. The delivery device can be a guide tube, a delivery sheath, a bronchoscope, or an endoscope and can include one or more viewing devices, such as optical viewing devices (e.g., cameras), optical trains (e.g., a set of lens), optical fibers, CCD chips, and the like. Once positioned in the desired region of the airway, such as the left and/or right main bronchi, the expandable member is expanded to position the one or more electrodes in contact with the airway wall.
Energy, such as RF energy, is supplied to the energy emitter to ablate the targeted tissue, causing a lesion to form, therefore temporarily or permanently damaging the targeted tissue, therefore affecting, e.g. attenuating nerve signals to or from, portions of the lungs associated with the targeted tissue. Simultaneously, a coolant is supplied through the catheter and is directed to the one or more electrodes and into the expandable member or balloon. This allows for cooling of the superficial tissue in contact with the electrode, as well as the adjacent tissues. The size, shape, and depth of the lesions are determined by the flow rate and temperature of the coolant, and the energy supplied to the energy emitter(s).
Devices, systems, and methods of targeted lung denervation are described in, for example, one or more of U.S. Pat. No. 8,088,127 to Mayse et al. and US Published Patent Application No. 2011/0152855 to Mayse et al., both of which are commonly assigned to the assignee of the present application and the disclosures of which are hereby incorporated by reference in their entireties.
One potential application of targeted lung denervation is treatment of the anterior pulmonary nerve plexus. An asthma treatment performed during the 1930's to 1950's, prior to the advent of effective asthma medications, was surgical sympathectomy of the posterior pulmonary nerve plexus. Although the surgery was very morbid, typically requiring severing large muscle groups and manipulating the ribs, pleura and lungs, it was in some cases effective.
There exists, in addition to the posterior pulmonary nerve plexus, an anterior pulmonary nerve plexus. Historically, the anterior pulmonary nerve plexus was never approached surgically due to its proximity to the heart and the great vessels. It is theorized that these nerves are also involved in airway constriction associated with asthma and other pulmonary diseases. There are several complicating factors to performing a denervation of these nerves from within the body. The nerves of interest run along the outside of the anterior trachea and bronchi, and the posterior plexus runs along the posterior, along and within the junction between the trachea and the esophagus. Damage to the esophagus or the branches of the vagus nerve that run along the outside of the esophagus and continue into the abdomen may be especially traumatic to a patient, and as a result of such difficulties there has historically been minimal interest in targeting the posterior and/or anterior pulmonary nerve plexus to treat pulmonary diseases.
Negative effects of ablation performed near the esophagus have been observed in association with cardiac ablation therapies, such as atrial fibrillation ablation therapies. These effects include esophageal fistulae and acute pyloric spasm and gastroparesis. Possible causes of these complications may be attributed to direct thermal energy delivered to esophageal tissue, injury to esophageal blood supply, late effects of an acidic environment within the esophagus, and/or injury to the vagus nerve and/or pulmonary nerve plexi.
In view of the risks of esophageal injury observed in cardiac ablation therapies, it would be advantageous if pulmonary-related ablation procedures could be performed near the esophagus without similar risks. Preferably such procedures would not only avoid injury to the esophagus directly, but injury to the peri-esophageal branches of the vagus nerve.
A need exists, therefore, for a solution to avoid injury to the esophagus during a pulmonary ablation procedure.